Women are twice as likely to have a child with autism if they have genital herpes during pregnancy

The study is the first of its kind to show the antibodies produced by a mum infected with genital herpes (HSV-2) – the sexually transmitted strain of the virus – may pose an increased risk of autism.

Milada Mahic, lead author of the study, said: “We believe the mother’s immune response to HSV-2 could be disrupting foetal central nervous system development, raising risk for autism.”

But the researchers, from the Centre for Infection and Immunity at Columbia University and the Norwegian Institute of Public Health, do not believe the risk is down to direct infection of the foetus.

Instead, inflammation in the mum’s body, in close proximity to the womb, is to blame.

There are about 35,000 cases of genital herpes in the UK per year – and most are in women.

We believe the mother’s immune response to HSV-2 could be disrupting foetal central nervous system development, raising risk for autism

Milada Mahiclead author of the study

After an initial outbreak, the genital herpes virus lives in nerve cells and is often inactive, with flare-ups occurring with diminishing frequency as the body builds up immunity to the virus.

The researchers sought to explore the link between maternal infection and risk for autism, focusing on five pathogens known collectively as ToRCH agents–Toxoplasma gondii, rubella virus, cytomegalovirus, and herpes simplex viruses type 1 and 2.

Exposure during pregnancy can lead to birth defects and even miscarriage.

They looked at blood samples from more than 400 mothers of children diagnosed with autism and almost 500 mothers whose children do not have autism.

The samples were taken at 18 weeks pregnant and at birth, then analysed for levels of the pathogens.

They found high levels of HSV 2, rather than any other pathogen, at early stages in the pregnancy correlated with children with autism.

It comes down to inflammation in the mother being in close proximity to the womb

In all, 13 per cent of mothers in the study tested positive for anti-HSV-2 antibodies at mid-pregnancy.

Of these, only 12 per cent reported having HSV lesions before pregnancy or during the first trimester, a likely indication that most infections showed no symptoms.

The effect of anti-HSV-2 antibodies on risk for ASD was only seen in baby boys, not baby girls.

Senior author Ian Lipkin said: “The cause or causes of most cases of autism are unknown.

“But evidence suggests a role for both genetic and environmental factors.

“Our work suggests that inflammation and immune activation may contribute to risk.

“Herpes simplex virus-2 could be one of any number of infectious agents involved.”

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But the National Autistic Society urged people not to worry unnecessarily about the study

Ian Dale, head of research at the society: “No-one should draw any firm conclusions from this study, which claims that women who are infected with genital herpes early in their pregnancy may be more likely to have a child on the autism spectrum. We urge people not to worry unnecessarily about this study.

“This study is the first to explore whether antibodies to genital herpes in pregnant women means their children are more like to be autistic, and further research is needed for any accurate conclusions to be made.

“We do not fully know what causes autism, however evidence suggests that it involves many factors, including genetics, the environment and the development of the brain.

“What’s most important for the 700,000 people on the autism spectrum in the UK today is to make sure that they have access to the right support from people who understand autism.”

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